For the manufacture of patterned paper like tissue products such as facial and bath tissue and paper towels or of other non-woven materials, it is known to use fabrics in the paper making machine being employed in making embossed or patterned paper webs products. One type of these fabrics are designed to be installed in the wet forming section of a paper making machine, where a fibrous pulp is deposited onto the paper side outer surface of this fabric (hereby called the paper side) of the forming fabric and is dewatered through the fabric with the help of gravity and suction boxes. At the end of the forming section, the so formed paper web is transferred to a dryer section, where the paper web is dried by applying heat and air streams.
A forming fabric for making embossed paper webs is disclosed in U.S. Pat. No. 6,237,644 B1. The fabric is embodied as a single layer weave having longitudinal or machine direction and transverse or cross machine direction threads interwoven with one another defining a machine side and a paper side. Some or all of the longitudinal threads form embossing threads having projecting paper side floats on the paper side passing over two or more successive transverse threads. Although it is indicated that the fabric can be embodied also as a multi-layer weave, U.S. Pat. No. 6,237,644 B1 does not disclose any example thereof.
Another fabric for the use in the wet forming section of a paper making machine is disclosed in EP 0 232 715 A1. This fabric consists of two superimposed weaves. The first woven fabric layer forming the paper side on its outside is embodied as a fine plain weave, while the fabric layer forming the machine side on its outside is designed coarser. The two layers are connected by additional binding threads or by structural (intrinsic) longitudinal and/or transverse threads of the first woven fabric layer. At the binding points, the first fabric layer is drawn to the second fabric layer thereby forming recesses in a desired pattern. These recesses cause according projections of high volume in the paper web on the surface adjacent to the paper side of the fabric.
In U.S. Pat. No. 5,429,686 A, a through-drying fabric for the drying section of a paper making machine is disclosed, which is intended to manufacture embossed paper webs, too. The fabric is designed as a single layer weave having longitudinal and transverse threads interwoven with one another. Some of the longitudinal threads form floats on the paper side passing over several transverse threads and thus forming elongated projecting paper side floats disposed in a parallel array and providing valleys between the floats. These floats and valleys form a reverse embossing into the adjacent surface of the paper web when dried in the drying section of the paper making machine.
Another through-drying fabric for creating elongated embossings in the paper web is disclosed in U.S. Pat. No. 5,713,397 A. The fabric comprises two superimposed fabric layers having longitudinal and transverse threads interwoven with one another, respectively. The two fabric layers are connected by structural (intrinsic) longitudinal yarns of the first fabric layer forming the paper side on its outside at selected binding points. Some or all of the longitudinal first threads form projecting paper side floats in a desired pattern causing valleys between the floats. The so structured paper side of the first fabric results in reversed embossings on the side of the paper web adjacently to the paper side of the fabric.
With the design of the fabrics as disclosed in the foregoing documents, it is not possible to manufacture paper webs with voluminous embossings. If that is desired, it is necessary to provide an additional coating on the paper side having recesses formed by through holes. However, this kind of fabrics is expensive to manufacture and has a drainage characteristic, which impairs the drainage of the paper web particularly when it is used in the wet forming section.